When the British decided to define the outer limits of their Indian empire, they fudged the question. After two disastrous wars in Afghanistan, they sent the Foreign Secretary of India, Sir Mortimer Durand, to Kabul in 1893 to agree the limits of British and Afghan influence. The result was the Durand Line which Pakistan considers today as its border and Afghanistan refuses to recognise. Then, rather than extend the rule of the Raj out to the Durand Line, the British baulked at pacifying the tribes in what is now Pakistan’s Federally Administered Tribal Areas (FATA). Instead, they used the still-extant Frontier Crimes Regulation of 1901 to keep them at bay, if necessary through collective punishment. The Pashtun tribes living on either side of the Durand Line continued to move back and forth, resenting outside interference and rejecting an arbitrary division of their lands by a foreign power.

The situation remains as nebulous to this day. Pakistan, like the British Raj before it, wants a secure western frontier and has been ready to back Islamist militants in Afghanistan to obtain it. Indeed, its emphasis on Islam has been used as a means of countering ethnic Pashtun nationalism, lest the Pashtun lay claim to a Pashtunistan covering both sides of the Durand Line. Meanwhile, remembering the days when Peshawar was a fabled Afghan city, some Afghans hanker after a Greater Afghanistan, incorporating the lands of all Pashtun (or Afghan) tribes as far as the Indus river. (Historically, the identification of Afghanistan with the Pashtun was such that the words “Afghan” and “Pashtun” were treated as synonyms.) And even those Afghans who recognise how unrealistic it would be to claim a sizeable chunk of modern-day Pakistan retain a proprietary sense over the Pashtun living on the other side of the Durand Line. Meanwhile the Pashtun themselves resent their arbitrary separation between two countries, which has reduced their capacity to exercise political power.

With the worsening of the Afghan war, the situation on either side of the Durand Line has become even more explosive. Islamabad complains about its sovereignty being breached by U.S. drone strikes in FATA; Kabul accuses Pakistan of sheltering and supporting Afghan Taliban militants on its side; Pakistan shells the Afghan provinces of Kunar and Nuristan where it says some of the Pakistani Taliban have taken refuge.

It was into this minefield that the United States stepped when – in what appeared to be almost a casual comment – U.S. special envoy for Afghanistan and Pakistan Marc Grossman reaffirmed during a visit to the region that Washington recognises the Durand Line as the international boundary. In case there were any doubts about what he said, State Department spokeswoman Victoria Nuland made the same point when asked at a briefing about the official U.S. position on the Durand Line. “Well, our policy on this has not changed,” she said. “It was correctly stated by Ambassador Grossman that we see this as the internationally recognised boundary.”

As someone who has been following Pakistan for a while, it came as a surprise to me that the United States had a policy on the Durand Line, given how contentious it is as an issue.

Grossman’s comments were first criticised by Afghanistan, and later played down as a reiteration of an existing position rather than a new approach:

“The Ministry of Foreign Affairs once again reaffirms the historic importance of the Durand Line for the Afghan people and reiterates its long-standing position that only the Afghan nation can determine its status,” the Afghan government said. “U.S. policy concerning the recognition of Durand Line is not a new development and has no bearing on the views of the Afghan people or the policy of the Government of Afghanistan on this issue.”

Grossman’s comments may indeed have been meant as no more than a passing reference to existing U.S. policy – Washington has little to gain by picking a fight with Kabul right now as it prepares to pull out most combat troops by the end of 2014 while negotiating the right to retain bases there afterwards which can be used for targeting al Qaeda and other Islamist militants, including through drone strikes in FATA. Yet arguments over the future of the Durand Line are not going to go away; rather they are likely to intensify as the deadline approaches for pulling out foreign troops from Afghanistan – especially if, as expected, there is no political settlement by then with Taliban insurgents. And as a result, even a throwaway remark about policy attracts attention.

At first glance, the idea of settling the border is appealing. With its western flank secured, Pakistan would have less reason to interfere in Afghanistan – though it would still worry about Indian influence there. Any agreement between Afghanistan and Pakistan would help them channel cross-border movement through official crossings while using joint surveillance and patrols to prevent Islamist militants moving back and forth. Islamabad would incorporate FATA fully into Pakistan and Kabul would breathe easier if it believed it were to be spared what is now more than 30 years of Islamist militants seeping in from the east.

But it is not that simple. Perhaps in the long-run, settling the border needs to be the ultimate aim. But it cannot be the starting point. Departing British colonial rulers proved when they partitioned India in 1947 that defining borders – without regard to, or consultations with, the people who lived on either side of them – only stored up bigger problems for later. Pashtun tribes on both sides of the Durand Line are already unhappy with governments in both Islamabad and Kabul – with the result that some support the same Islamist militancy which, ironically, was once nurtured by Pakistan to suppress Pashtun nationalism. On both sides they believe they have been marginalised – in Afghanistan following the U.S.-led invasion which ousted the Pashtun Taliban; and in Pakistan by the dominance of the country’s heartland Punjab province. Without accommodating ethnic Pashtun fully in the political processes of both Afghanistan and Pakistan before agreeing a frontier, the imposition of a border – itself going against cherished rights of free movement and trade – could stoke more, rather than less violence.

And legally, the case for turning the Durand Line into the international border is not watertight. Pakistan argues that it is the clear inheritor of borders negotiated by the British before 1947; Afghanistan has a multitude of grievances with the Durand Line, one of which is that it says the treaty was forced upon it by British imperialism.

In a review of historical documents on the original 1893 agreement and published by RUSI (subscription), authors Bijan Omrani and Frank Ledwidge conclude that the Durand Line was never meant to be an international border.

The research paper argues that the agreement negotiated by Durand with Afghan Amir Abdur Rahman fixed only “the limit of their respective spheres of influence” rather than being a clear delineation of sovereignty. It quotes a memorandum written by Sir Denis Fitzpatrick, the Lieutenant-Governor of Punjab and therefore the most senior official overseeing the frontier at the time, writing in 1896 that:

“I think it is of the highest importance that it should simply be understood to be a line on our side of which the Amir’s interference except when we allow him to chastise a tribe, shall be absolutely excluded … I think if the agreement between us and the Amir were treated to be anything like a partition of territory, it would have a bad effect…”

The paper also notes that should a dispute over the recognition of the Durand Line ever be taken to international arbitration, a court would need to examine whether both countries had treated it as an international border for a prolonged period – evidence that would be nearly impossible to provide given the degree of interference and movement of people on both sides.

Intriguingly, given Pakistan’s own deep hostility to U.S.-led or Afghan raids into FATA to tackle Taliban militants, the paper also argues that such “hot pursuit” was clearly allowed in the original treaty. It quotes Fitzpatrick as saying that, “There would be places in which for a long time to come we should not attempt to establish internal peace or prevent the tribes from fighting amongst themselves and places like the Afridi country where it would be difficult for us to prevent the tribes from raiding on the Amir’s territory and in which accordingly we should in a proper case have to allow the Amir to counter-raid, though on the understanding that he would not take permanent possession.”

Going by that interpretation of the treaty – and other historians and other lawyers, reading different documents in different languages might read it differently – you could make a case that Afghanistan (and the United States if acting on behalf of Kabul) could conduct raids by ground troops into FATA. Equally, Pakistan could send troops into Kunar and Nuristan. It is a can of worms that nobody has wanted to open – the anecdote serves not to prove a point of law or history but rather to illustrate the complexity of the Durand Line question.

The paper finishes by recommending that rather than stick to an artificial 19th century line, Afghanistan and Pakistan should work out a means of shared sovereignty, recognising the needs of the people who live there, closely linked by family ties and custom, to move and trade freely across the Durand Line. “…the best way to solve the many problems on either side of it – poverty, illiteracy, poor health, corruption, terrorism, laws which contravene all notions of human rights – is not to persist in the attempt to split sovereignty, but to share it. An area so unified in terrain, population and custom cannot bear inequalities in administration, but requires a common approach on both sides to solve the problems.”

Maybe; maybe not. It is hard to see how this could work at a time when Taliban militants are bent on taking over both Afghanistan and, more recently as far as the Pakistani Taliban are concerned, Pakistan as well. In any case, the trust is not there between Pakistan and Afghanistan to even begin to consider such an arrangement.

But perhaps there is a need for outside, UN, mediation. This is too difficult an issue to be resolved by a few short words from the United States that “we see this as the internationally recognised boundary.”

The tribal areas have changed massively since the days of the British and we should be very wary of summoning their experience. Yet we should also be aware of it.

Here is what the research paper describes as the response to the Durand Line agreement: “Reaction amongst the Pashtun tribes to the demarcation was generally (though with a few exceptions) negative. The Mahsuds attacked and burned the British Boundary Commission camp in Wana (in South Waziristan) in 1894, and in 1897, after the conclusion of the Commission’s work, there was a general rising which required the action of 60,000 troops to suppress.”